The public sewerage system is out of repair and leaking to a considerable extent, namely of approximately 15 to 20 per cent. This causes considerable pollution, in particular of ground water and drinking water. Repair of these damages requires great efforts.
The book of Stein and Niederehe, "Instandhaltung von Kanalisationen" (Sewerage System Maintenance), Ernst & Sohn Verlag, Berlin 1987, pages 308 to 317, discloses numerous methods of repairing or reconstructing damaged sewer pipes that consist in sealing the sewer pipes located in the ground.
The so-called injection method consists in sealing leaking pipe connections by an injection of acrylic resins into the pipe. In another sealing method gaskets are manually inserted into the sewer pipe and pressed against the inside wall of the sewer pipe by means of steel pressing rings. A relining method consists in that a defined annular space is produced with the aid of reusable tube formwork provided with spacers and in that cement mortar is pressed into this space. In a further lining method cement mortar is placed between a pressure piston and a displacement body. When this device is pulled through the sewer pipe, the mortar is pressed against the pipe wall by the displacement body. In a further relining method the relining material is centrifuged towards the inside wall of the sewer pipe by a centrifugal head rotating at high speed.
So-called pipe-line relining consists in a plastic pipe being introduced into the sewer pipe to be reconstructed, which reduces the pipe cross-section considerably. The remaining annular space is filled. Excavations are necessary where break-throughs have to be produced in the continuous plastic pipe for house or street connections.
In the method of so-called short-pipe lining short single pipes are individually entered via an inspection pit into a sewer pipe to be repaired. This also reduces the sewer cross-section. The remaining annular space is filled as a rule. Excavations are necessary to produce house or street connections.
In the so-called wrapped-tube relining method wrapped tubes produced at site from plastic profile strips are entered into the sewer pipe to be repaired. The annular space is filled as a rule.
The so-called hose relining consists in that a prefabricated felt hose soaked with synthetic resin is introduced into the sewer line to be repaired and is pressed to the inside wall of the sewer pipe by internal pressure. Curing is effected in situ by heat supply. House and street connections must be cleared by milling.